Mircea Voskerician says he agreed to sell his stake in the property to Zuckerberg in exchange for a promise that Zuckerberg would introduce him to other wealthy people who might want to buy homes. Voskerician says Zuckerberg never made those introductions.

His lawsuit, filed this month in Santa Clara County, claims breach of contract. The San Jose Mercury News reported the lawsuit Monday.

Zuckerberg's attorney, Patrick Gunn, told the Mercury News his client paid Voskerician $1.7 million for the right to buy the property. He says Voskerician's lawsuit is meritless.

The Facebook CEO Mark Zuckerberg paid over $43 million in separate deals to buy four homes and lots adjoining his house in the tony Crescent Park neighbourhood of Palo Alto in late 2012 and 2013 after learning that a developer planned to build a large house behind his existing home.

"Zuckerberg stated he did not want construction in his backyard for 14 months and told Voskerician that he would refer him business and make him introductions if, in exchange, Voskerician would help him secure his privacy," the lawsuit states.

Zuckerberg reaped a $3.3 billion gain last year by exercising stock options in the social networking company that he founded in a Harvard University dorm room.

Mark Zuckerberg and his wife, Priscilla Chan, were the most generous American philanthropists in 2013, with a donation of 18 million shares of Facebook stock, valued at more than $970 million, to a Silicon Valley nonprofit in December.